Speed-regulator for electric motors



XVILLIAM lV. ASCHIFFMANN,

PATENT lirici-3'.

OF ST. PAUL, MINNESOTA.

SPEED-REGULATOR FOR ELEOTRlC MOTORS.

SPECIFICATION forming part of Letters Patent No. 442,208, dated December 9, 1890.

Application led April ZS, 1890. Serial No. 349,797. (No model.)

To all whom it may concern.-

Be it known that I, IVVILLIAM WV. SCHIFF- MANN, a citizen of the United States, residing at St.Paul,in the county ot Ramsey and State of Minnesota, have invented certain new and useful Improvements in Electrical Motor Speed-Regulators, of which the following is a specification.

rlhis invention relates to speed-regulators for apparatus operated by electrical motors; and it consists in the construction and adaptation of parts, as hereinafter shown and described, and specifically pointed out in the claims.

This invention may be applied to many different forms of apparatus driven by electrical motors wherein a variable speed is required; but for the purpose ot illustration I have shown .it applied to the hand-piece of a dental engine, to which form of apparatus the invention is peculiarly applicable.

In the drawings, Figure l represents the hand-piece of a dental engine with my improved regulating device arranged therein. Fig. 2 is a cross-section on the line X X ot Fig. l. Fig. 3 is a cross-section on the line Y Y ot Fig. l. Fig. e is a longitudinal section of a portion ot' the hand-piece, showing the arrangement and location or" the contactplates therein. Fig. 5 is a similar view showing the location and arrangement of the reversing mechanism or switch. Fig. 6 is a cross-section, enlarged, of the lexible shaft connecting the hand-piece with the driving mechanism of the motor, showing the manner of arranging the conducting-Wires therein. Fig. 7 is a detail diagram View of the difterent parts, illustrating the wiring system and connections. Fig. 8 is a detail diagram View similar to Fig. 7, but on a smaller scale, illustrating more completely the manner ot' arranging the wiring and connecting the motor and the hand-piece.

A represents the casing of the hand-piece of a dental engine,` A2 the burr,7 and A3 a section of the exible shatting by which the burr or other implement is driven, all these parts being of the usual construction. 'lhe grip part A4 of the hand-piece is formed hollow and with a core a, and has partially embedded in vits core a number of contactplates of regularly-graduated lengths. These plates will correspond in number with the different speeds at which the motor is desired to be run, with one plate additional as a dead or negative wire. For the purpose of illustration I have shown four ot'.these contact-plates b b2 b3 b4, the lirst one h being the longest and representing the dead or negative wire, and b4 the shortest and representing the greatest speed,while the contactplates b2 and h3 represent the intermediate speeds.

B represents a rheostat or assembly of resistance-coils, and D an electric motor placed at anyconvenient point with reference to the dental engine. The motor is adapted to drive the shal't journaled in the hand-piece A by means ot' a flexible shaft and a system of pulleys in any suitable manner, and for the purpose of illustrationI have shown the outline ot such a system in Fig.`8, in which d represents a cord belt running from the motor D over pulleys d2 to the flexible shaft A3, while the conducting-wires between the` hand-piece and the rheostat and motor are placed inside the envelope of this iexible shalt, as hereinafter more fully described. The contact-platesh b2 b3 h4 are connected by conducting-wires to the rheostat. The plate h isconnected to conducting-Wires h5, which pass through the binding-post t 'on the rheostat and thence to the fieldmagnet F of the motor, while the plate b2 is connected by conducting-wire b to the plate e on the rheostat, which is connected into the longest series of coils and represents the greatest resistance, while the next plate h3 is connected by conducting-wire 197 to the next plate e2 on the rheostat, which is connected into a shorter system of resistancecoils and represents a less resistance than the plate e', while the next plate h4 is connected by conducting-wire 11S to theneXt plate e3 on the rheostat, which is connected directly to the main negative-current wire N, so that there is no resistance whatever to the current passing through the plate b4 andwire hs. rlhe rheostat shown is of the ordinary construction, such as are in common use, but without a switch or speed-controlling arm, as with my invention this part of the instrument is not used. These wires b5 h6 t7 bs are conducted from the hand-piece A inside the IOO covering A2, surrounding the flexible shaft, as shown in Figs. l, G, and 8, and from thence within a suitablyinsulated covering to the rheostat, so that none of the wires are exposed in their transit.

In Fig. 7 I have shown a diagram illustrating more fully the course of the different wires and the connections, P representing the positivewire, which passes through the eld magnet F2.

H represents a circuit-closin g plate adapted to rest across the contact-plates Z1 Z22 bsbl, and provided with an insulated knob H2, by which it may be moved, the knob projecting through a slot m in the shell oi' the grip part A4 of the hand-piece, so as to be readily actuated by the person using the implement.

Along the edge ol' the slot m are a series of lines fm2, corresponding to the lengths of the plates b b2 b2 Z9, to denote the position of the plate I-I. Thus when the knob H2 is opposite the mark m2 nearest the burr A2 the plate H will be resting across all the plates b b2 b2 Z)A1 and forming an electrical connection with the wire b5, leading' directly from one magnet of the motor, with the wire bs leading directly to the negative wire N, using the full current and causing the motor to run at full speed, and then if the knob 11,2 be placed as shown in Figs. l and 7 Vthe plate b2 will be connected to the plate Z2', and the wire lf, leading from one ot the magnets of the motor, will be connected with the wire Z1, leading through the longest series ot' the resistancecoils in the rheostat, before passing' into the main negative wire N, and thus checking the motor and causing it to run at its slowest speed. Then it' the knob H2 be placed opposite the mark m2 farthest from the burr the motor will be stopped entirely, as the plate ll will rest only in contact with the plate Z1 and break the current between the wires Zf and Z1 or Zor b2. It will thus be readily seen that any desired speed may be maintained by increasing the number of the contact-plates connected to the rheostat and increasing the scope ol' the resistance-eoils therein.

It is frequently necessary to reverse the motion of the burror other implement which is being used in the hand-piece, and to do this quickly and effectively I arrange within the grip A'1 a reversingswitch, as shown. This consists of four contact points or plates 'L t2 'i2 t, the points t" t connected by a loop i' and the points 'L2 r2 connected by a loop t'. The point t" is connected by conducting-wire if to one of the ieldanagnets F2 of the motor, while the point 'i2 is connected by conducting-wire 2 to the other field-magnet F of the motor.

G G2 represent two pivoted bars connected together by an insulated cross-bar having a knob G2 and adapted to rest by their ends upon the points i" i2 or upon the points z2 or fr, according as the bars are moved to the right or left. The'bar G is connected by conducting-wire if to one brush F2 of the commutator of the motor, while the other bar `1'2 is likewise connected by conducting-wire "2 to the other brush F'1 ot' the commutator. Zhen the bars G G2 are placed as shown in Figs. 5 or 7, the current passes through the motor in one direction, causing it to run in one direction, and when the position of the bars G G2 is reversed the current passes through the motor in the opposite direction and reverses it. This is a very import-ant feature ot' this invention, as it is frequently necessary to reverse the motion of the burrs` in dental work, many burrs being made to cut in both directions. This reversing feature is especially advantageous when arranged as herein shown, so that it can be easily accomplished by one of the fingers or the thumb of the hand holding the implement and without the necessity for releasing the hand from the iinplement or changing its relation thereto. The knob G2 passes upward through a slot in the shell of the grip part Al of the hand-piece in a similar way to the knob H2. By this simple construction the motor can be perfectly controlled by merely adjusting the two small knobs H2 G on the bridging-plate lil. and upon the switch-bars G G2, and when placed within the hand-piece of a dental engine the operator is enabled to easily manipulate it by the lingers of the saine hand which holds the hand-piece, so that there is no necessity for him to remove the implement from its work or release the hand engaged with the patient.

Another important feature of this invention is in passing all the conducting-wires between the hand-piece and the motor and rheostat within the casing or envelope of the flexible shaft, as the wires are thereby concealed from sight and are not exposed to the danger of loss by leakage or from other sources.

llfaving thus described my invention, what I claim as new isl. In a dental-engine hand-piece, a series of graduated contact-plates embedded therein and in electrical connection with a rheostat, a motor in electrical connection with said rheostat and adapted to actuatc the sha-'ft ot' said hand-piece, a commntator adapted to be moved over said contact-plates, said graduated contact-plates and placed near the outer or burr end of said hand-piece, so that said commutator may be actuated by the iingers or thumb of the hand which holds the hand-piece and without releasing its hold therefrom or changing its relation thereto.

2. In a dental-engine hand-piece, a series ci' graduated contact-plates embedded in the hand-piece near its burr end in electrical connection with a rheostat, a motor in electrical connection with said rheostat and adapted to aetuate the shaft of said hand-piece, a commutator adapted to be moved over said contact-plates, a reversing-switch embedded in said hand-piece near said contact-plates and connected into the circuit of said motor,

commutator being IOO IIC

whereby said commutator and switch may In testimony whereof I have hereunto set be actuated by the lingers 01 thumb of the my hand in the presence of two subscribing hand which holds the hand-piece, and the Witnesses.

speed and motion of the burr controlled With- XVILLIAM W. SCHIFFMANN. out releasing the hand or changing the rela- Witnesses: tion to the hand-piece, substantially as and C. N.v WOODWARD,

for the purpose set forth. H. S. WEBSTER. Y`\ 

